This invention relates to an automatic shoe clearance adjustment device for a drum brake device equipped with an over-adjustment preventive measure which suspends the adjustment operation when the brake temperature rises.
In traditional automatic shoe clearance adjustment devices for a drum brake device, an opening action of the two facing plates of a folded bimetal member provided at the strut restricts the over-adjustment operation in case the brake drum expands as the brake temperature rises. One example is shown in Japanese Patent Publication Number Showa 58-49739.
Yet, in the above-described device, simply, a tube of the strut fits over the screw rod with a gap therebetween. Hence, until the strut is actually placed between the brake shoe and the hand brake lever and until the return spring is fitted, the strut could freely come out in the direction of that axle and could freely rotate.
Then, a rib of the folded bimetal member is structurally apt to come out from a triangle-like concave portion of the tube. For this reason, assembling the strut, in which the concave portion of the rib is interlocked, is said to be difficult.
If the strut is assembled while the rib is dislocated off from the concave portion of the tube, due to a large thrust force on the strut while the hand brake lever is in operation, the rib is deformed and may adversely affect the automatic adjustment operation which requires a delicate adjustment operation. Also, the same type of adverse effect may occur if the folded bimetal member rotates to interfere with other parts such as the shoe return spring. In addition, even if the misassembled parts are fortunately found, a correction of the misassembled parts demands effort and time.